Air powered actuator for retracting the locking pins of a slider

ABSTRACT

An air powered actuator is provided for exerting sufficient force on the locking pins of a slider for the adjustment of the suspension of a vehicle longitudinally with respect to the body of the vehicle. The air powered actuator is controlled from the cab of the vehicle. A signal light is illuminated when the locking pins of the slider have been completely retracted. A position sensor is provided which deactivates the signal light each time the trailer is moved a predetermined amount with respect to the slider.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part application of application Ser. No.08/195,852 filed Feb. 10, 1994, entitled "AN AIR POWERED ACTUATOR FORRETRACTING THE LOCKING PINS OF A SLIDER".

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a slider which is used to adjust thesuspension of a vehicle longitudinally with respect to the body of thevehicle, and more particularly to an air powered actuator for retractingthe locking pins of the slider.

2. Background of the Invention

Sliders are commonly used to enable longitudinal adjustment of thesuspension of a tandem axle trailer relative to the van or body of thetrailer. Conventional sliders normally comprise a pair of side railswhich are secured to the left and right sides of the van and whichextend longitudinally therealong the underside thereof. The suspensionof the trailer is carried by a frame which includes left and right slidemembers which are slidably mounted with respect to the side rails of thevan. A plurality of locking pins lock the frame in various positionswith respect to the side rails. When it is desired to adjust thesuspension of the trailer with respect to the body, the locking pins areretracted to permit the frame to slide with respect to the side rails ofthe van. However, if the vehicle is not sitting on perfectly levelground, the locking pins may be difficult to pull from their registeringopenings in the frame and the side rails of the body. Heretofore, thenormal procedure for freeing the locking pins was to have one personpull on the actuating arm connected to the locking pins while the driverattempted to jiggle or jog the trailer with respect to the tandem axle,which had been previously locked in place with the air powered emergencybrake. The above solution was not satisfactory and an effort to solvethe problem is disclosed in U.S. Pat. No. 4,838,566. Although it isbelieved that the device of the '566 patent makes the problem describedabove easier to solve, it is still believed that the device disclosed inthe '566 patent does not completely solve the problems of retracting thelocking pins from their registering openings in the frame and the siderails of the trailer.

The invention disclosed in the co-pending application represented asignificant advance in the art. However, the invention described in theco-pending application did not include any means which would indicate tothe vehicle operator that the locking pins had been completelyretracted. Further, the invention of the co-pending application did notinclude any means for indicating the relative position of the vehiclebody with respect to the vehicle suspension as the vehicle body is beingmoved with respect to the vehicle suspension.

SUMMARY OF THE INVENTION

The invention described herein is an improvement over the slider of U.S.Pat. No. 4,838,566 in that an air powered actuator is operativelyconnected to the locking pin interconnects so that air pressure may beutilized to pull the locking pins from their registering openings in theframe and the side rails of the trailer. In operation, when it isdesired to longitudinally adjust the suspension of the trailer withrespect to the trailer body, the emergency brake for the tandem axle isfirst set or activated. The air powered actuator is then actuated whichexerts sufficient retracting force on the locking pins to pull thelocking pins from their registering openings in the frame and the siderails of the trailer.

In the invention described herein, a light is positioned either at theside of the vehicle body or at some other convenient location which isvisible to the vehicle operator during the adjustment of the vehiclebody with respect to the vehicle suspension. The light is controlled bya switch mounted on the slider which is actuated only when the lockingpins have been fully moved to their retracted positions to indicate tothe operator that the locking pins are in their retracted positions.Further, the instant invention includes means which deactivates thesignal light at the side of the trailer each time the vehicle body ismoved a predetermined amount with respect to the vehicle suspensionduring the adjustment process so that the operator will be able toascertain the location of the trailer with respect to the suspension.

It is therefore a principal object of the invention to provide animproved slider for adjustment of the suspension of a trailerlongitudinally with respect to the body of the trailer.

A further object of the invention is to provide an air powered actuatorfor retracting the locking pins of a slider.

A further object of the invention is to provide an invention of the typedescribed above which may be easily connected to the conventional slideradjustment actuator without extensive modification thereof.

Still another object of the invention is to provide a device of the typedescribed above which is safe to use.

Still another object of the invention is to provide a device of the typedescribed above which is convenient to use.

Still another object of the invention is to provide an invention of thetype described above which is economical of manufacture and easy toinstall.

Yet another object of the invention is to provide an invention of thetype described above which includes a signal means which is actuatedonly when the locking pins of the slider have been fully retracted.

Still another object of the invention is to provide an invention of thetype described above including a signal means which is successivelyactuated upon predetermined movement of the vehicle body with respect tothe vehicle suspension during the adjustment procedure.

These and other objects will be apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial side view of the suspension system of a trailerhaving a tandem axle;

FIG. 2 is a front view of the trailer of FIG. 1;

FIG. 3 is an exploded perspective view of the air powered actuator ofthis invention;

FIG. 4 is a front view of the slider adjustment assembly and the airpowered actuator of this invention;

FIG. 5 is a front view of the air powered actuator of this inventionwhich illustrates the air powered actuator in its non-actuatingposition;

FIG. 6 is a view similar to FIG. 5 except that the air powered actuatorhas been actuated;

FIG. 7 is a partial top view of the air powered actuator of thisinvention and its relationship with respect to the slider assembly;

FIG. 8 is a schematic of the circuitry for the air powered actuator ofthis invention; and

FIG. 9 is a perspective view of the mechanism which successivelydeactivates a signal light to indicate movement of the trailer body withrespect to the trailer suspension.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The numeral 10 refers generally to a trailer which is conventionallypulled by a truck or tractor having a fifth wheel connection thereto.Trailer 10 includes a frame 12 having a plurality of transverselyextending cross frame members 14 extending between the sides thereof. Aslider 16, such as disclosed in U.S. Pat. No. 4,838,566, is secured tothe underside of the cross frame members 14 near the rear end of thetrailer 10. The numeral 18 refers to a tandem axle suspension which isoperatively connected to the slider 16 for movement longitudinallytherewith with respect to the trailer 10.

Slider 16 includes a pair of side rails 20 and 22 which are secured tothe underside of the cross frame members 14. Side rail 20 is generallyZ-shaped and includes a top flange 24, bottom flange 26 and asubstantially vertically disposed web 28 interconnecting flanges 24 and26. As seen in FIG. 5, side rail 22 includes top flange 30, bottomflange 32 and a substantially vertically disposed web 34 whichinterconnects the flanges 30 and 32.

Slider 16 also includes a rectangular frame, generally designated by thereference numeral 36 in FIG. 7, which carries the suspension of thetandem axle and which includes left and right slide members 38 and 40.The slide members 38 and 40 are slidable longitudinally of the van ortrailer on the side rails 20 and 22. As is best illustrated in FIG. 4,each of the slide members 38 and 40 are of generally G-shaped insection. Slide member 38 includes an upper inwardly-directed horizontalflange 42 spaced below the upper flange 24 of the side rail 20, agenerally vertical side wall 44 disposed inwardly of the web 28 of aside rail, a lower inwardly directed horizontal flange 46, and a lip 48bent inwardly from the inner end of the lower flange 46. Similarly,slide member 40 has an upper inwardly-directed horizontal flange 50spaced below the upper flange 30 of side rail 22, a generally verticalside wall 52 disposed inwardly of the web 34 of the side rail 22, alower inwardly-directed horizontal flange 54, and a lip 56 bent inwardlyfrom the inner end of the lower flange 54. Slide members 38 and 40 areprovided with upright reinforcing gussets 58 and 60 respectively, theend result being that each slide member 38 and 40 is a hollow-beammember.

A plurality of hook-shaped sliders 62 are secured to the side wall 44 ofthe slide member 38 and overlie the lower flange 26 of the side rail 20as illustrated in FIG. 4. A plurality of hook-shaped sliders 64 aresecured to the side wall 52 of the slide member 40 and overlie the lowerflange 32 of the side rail 22. The hook-shaped sliders 62 and 64 permitthe frame 36 of the slider 16, carrying the suspension, to be slidablylongitudinally adjusted relative to the side rails 20 and 22. Pad 66 isprovided between the upper flange 42 of slide member 38 and the upperflange 24 of side rail 20 to ensure a relatively close sliding fitbetween the two members. A pad 68 is provided between the upper flange50 of slide member 40 and the flange 30 of side rail 22 to also ensure arelatively close sliding fit between the two members. Cross beams 70 and72 are secured to and extend between the slide members 38 and 40 andextend therebetween. In particular, the cross beams 70 and 72 aresecured to the gusset plates 58 and 60.

A plurality of locking pins, each designated with the reference numeral74 are provided for locking the frame 36 in various positions ofadjustment relative to the side rails 20 and 22. Four such pins areillustrated in FIG. 7, two at the front of the slider 16, adjacentopposite slide members 38 and 40, and two at the rear of the slideradjacent opposite slide members 38 and 40. The locking pins 74 aresupported by mounting plates 76 secured to the cross beams 70 and 72 forhorizontal linear movement in a direction generally transverse to thetrailer and are conjointly retractable for permitting adjustment of theframe 36 to various positions of adjustment relative to the side rails20 and 22 and extensible for locking the frame 36 in a selected positionof adjustment. When a pin 74 is in its extended position, it extendsthrough an opening in gusset 58 and through an opening 80 in therespective side wall of the respective slide member 38 or 40. Lockingpin 74, when in its extended position, also extends through one of aseries of openings 82 in the web of the respective slide member 38 or40. The openings 82 are spaced at regular intervals to provide thenecessary adjustment. Each pin 74 is biased towards its extendedposition by means of a spring 84 disposed between the mounting plate 76and a radial flange 86 around the pin towards its outer end.

The locking pins 74 are conjointly movable between extended andretracted positions by means of linkage generally indicated at 88interconnecting the pins. The linkage 88 comprises a shaft 90 extendinglongitudinally of the frame generally parallel to the slide members 38and 40 and approximately midway therebetween. As illustrated in FIG. 7,shaft 90 is journaled in cross frame members 70 and 72 for rotation aswill be described hereinafter. A plurality of links 92, one for eachlocking pin 74, interconnect shaft 90 and the pins 74. As illustrated inFIG. 4, the inner ends of the links 92 connecting the two locking pins74 at the rear of the slider are pivotally connected to opposite ends ofplate 94 which is secured to the shaft 90, and the outer ends of theselinks are pivotally connected to their respective pins 74. Thus, whenshaft 90 is rotated in a first direction, the links 92 will pull thepins 74 from their extended positions to their retracted positions.Conversely, when the shaft 90 is rotated in a direction opposite to thatjust described, the links 92 will move the pins 74 towards theirextended positions. The springs 84 on the locking pins 74 urge thelocking pins 74 to their extended positions.

An actuating chain 96 is provided for conventionally rotating the shaft90 thereby affecting articulation of the links 92 to retract the lockingpins 74. In U.S. Pat. No. 4,838,566, the chain 96 is in the form of arod. The chain 96 extends generally transversely with respect to thetrailer and laterally outwardly through the slide member 38. Aspring-loaded linkage 98 interconnects the inner end of the chain 96 andthe shaft 90 for a purpose which is described in U.S. Pat. No.4,838,566. It should be noted, that all of the structure previouslydescribed is conventional structure, except for chain 96 beingsubstituted for a pull rod, which is disclosed in U.S. Pat. No.4,838,566. It is the structure described above which applicant believesdoes not perform satisfactorily thereby necessitating the means of thisinvention to power rotate the shaft 90 to positively cause theretraction of the locking pins 74.

For purposes of description, the air powered actuator of this inventionis referred to generally by the reference numeral 100. It should benoted that although the air powered actuator 100, which will now bedescribed, is ideally suited for use with the slider described in U.S.Pat. No. 4,838,566, the air powered actuator 100 of this invention maybe easily adapted for use with any slider employing retractable lockingpins. For example, the air powered actuator of this invention couldeasily be modified to operate the locking pins disclosed in U.S. Pat.Nos. 2,935,332; 2,978,051; 3,146,000; 3,365,211; 3,372,946; 3,778,079;or 4,838,578.

Air powered actuator 100 includes a pressure cylinder or canister 102 ofconventional design having a rod 104 extending from one side of thehousing 106. Threaded studs S and S' extend from one side of housing106. Housing 106 has an air inlet 108 which is connected to a source ofair under pressure as will be described hereinafter. When air underpressure is supplied to the housing 106, the rod 104 is extendedtherefrom in conventional fashion. Preferably, the pressure cylinder 102is of the type which is normally associated with vehicle air brakes.Although it is preferred that the pressure cylinder or air brake 102 beutilized, the pressure cylinder 102 could be replaced by any suitablefluid cylinder, fluid motor, etc., wherein a movable rod, similar to rod104, extends therefrom when air or fluid pressure is supplied to thedevice.

Rod 104 has a clevis 110 mounted thereon which extends through bracket112 which is secured to the studs S and S' of housing 106 by nuts 114and 116. Bracket 112 includes a pair of spaced-apart arms 118 and 120having elongated slots 122 and 124 formed therein respectively. Theouter ends of the arms 118 and 120 have a bushing 121 which receives abolt 128 to pivotally secure the bracket 112 to bracket 126. Bracket 126is secured to the slide member 38 by bolts 129. Bushing 121 may eitherbe positioned in alignment with the openings 0' or the openings 0" topermit the actuator to be mounted on various sizes of equipment.

Pin 130 is slidably received in the slots 122 and 124 and is maintainedtherein by means of the washers 132 and 134 positioned on the outer endsthereof outwardly of the arms 118 and 120. Retaining key 136 is receivedin one end of the pin 130 to maintain the washer 134 on the pin 130.

Link 140 is provided which has an opening 142 at one end thereof whichrotatably receives the pin 130. As seen in the drawings, link 140 isrotatably mounted on the pin 130 between the arms 118 and 120. Link 140is provided with an opening 144 at its other end which receives a bolt146 to enable link 140 to be pivotally secured to a semi-circularbracket member 148. A semi-circular bracket member 150 is adapted to besecured to the bracket member 148 by means of the bolts 152 and 154extending through openings 156 and 158 in bracket member 148 andopenings 160 and 162 in bracket member 150. Bracket members 148 and 150are adapted to be secured to the shaft 90 which will have been drilledto provide a pair of openings extending therethrough so that the bolts152 and 154 may be extended therethrough.

The numeral 164 refers to a microswitch having a housing 166 which issecured to arm 118 by means of bolts 168 and 170. Microswitch 164includes a switch arm 172 extending therefrom which is in the movablepath of the pin 130 as illustrated in FIGS. 5 and 6. When the airactuator is actuated and the pin 130 moves outwardly in the slots 122and 124, which means that the locking pins have been fully retracted,the light 175 at the side of the vehicle, or other convenient location,will be illuminated as will be described in more detail hereinafter toindicate to the driver that the locking pins have been fully retracted.

FIG. 5 illustrates the rod 104 of cylinder 102 in its normal retractedposition. With the rod 104 in the retracted position, the links 92 arein the position so that the locking pins 74 are in their locked orextended position. When it is desired to retract the locking pins 74 toenable the suspension of the trailer to be longitudinally moved withrespect to the body of the trailer, air is supplied to cylinder 102 sothat rod 104 is extended therefrom. As rod 104 is extended from thecylinder 102, pin 130 is moved laterally outwardly in the slots 122 and124. The outward movement of the pin 130 in the slots 122 and 124 causesthe link 140 to be pivoted which in turn causes the bracket 148 to bepivoted which causes the shaft 90 to be rotated from the position ofFIG. 5 to the position of FIG. 6. The rotational movement of the shaft90 causes the plate 94 to be rotated which causes the links 92 toretract the locking pins 74.

In the event that the locking pins 74 are stuck in their respectiveopenings, due to some binding force thereon, the rod 104 may not be ableto be extended by the pressure exerted in the pressure cylinder 102.However, with air pressure being maintained in the cylinder 102, outwardforce or pressure is applied to the rod 104. The operator of the vehiclethen slightly "jogs", "jiggles" or moves the trailer with respect to thetandem axle suspension. As soon as the trailer has been sufficientlymoved to relieve the binding forces on the locking pins 74, the outwardpressure being exerted on the rod 104 will cause the shaft 90 to berotated so that the locking pins 74 are retracted. At that time, light175 will be illuminated as will be described hereinafter.

An electrically operated air valve 174 is operatively connected to theair inlet 108 of the cylinder 102 and has an exhaust port 176 extendingdownwardly therefrom. An air regulator 178 is provided on the inlet sideof the air valve 174 and is connected to an air line 180 which isconnected to the air line 182 as illustrated in FIG. 8.

Air valve 174 is controlled by a switch 184 located on the dash in theoperator's cab. When the switch 184 is closed, the air valve 174 isactuated, as is the indicator light 188, to indicate to the operatorthat the system is being operated to retract the locking pins 74. Anaudible signal device 190 is also actuated when the switch 184 is closedto further indicate to the operator that air is being supplied to theair actuator. The control or supply of air to regulator 178 and valve174 is controlled by the air brake control for the brakes on the reartandem axle. As seen in FIG. 8, the brake control lever 192 is actuatedto supply air to the brakes on the rear tandem axle to lock the reartandem axle in position. At the same time, air is supplied to the inletside of valve 174. Air is supplied from the valve 174 to cylinder 102when the normally open switch 184 is closed.

In operation, to summarize somewhat, when it is desired to adjust thesuspension of the rear tandem axle of the trailer with respect to thebody of the trailer, lever 192 is actuated to supply air to the brakeson the rear tandem axle to lock the rear tandem axle in position. At thesame time, air is supplied to the valve 174. The closing of the switch184 causes the valve 174 to be opened so that air is supplied to theinlet side of the cylinder 102. At this time, the indicator light 188and the audible signal device 190 are actuated to indicate to theoperator that air is being supplied to the cylinder 102.

When valve 174 is opened, air is supplied to cylinder 102 so that rod104 is extended therefrom. As rod 104 is extended from the cylinder 102,pin 130 is moved laterally outwardly in the slots 122 and 124. Theoutward movement of the pin 130 in the slots 122 and 124 causes the link140 to be pivoted which in turn causes the bracket members 148 and 150to be pivoted which causes a shaft 90 to be rotated from the position ofFIG. 5 to the position of FIG. 6. The rotational movement of the shaft90 causes the plate 94 to be rotated which causes the links 92 toretract the locking pins 74.

In the event that the locking pins 74 are stuck in their respectiveopenings, due to some binding force thereon, the pin 30 will not be ableto move outwardly in the slots 122 and 124. Since pin 30 is unable tomove outwardly in the slots 122 and 124, due to the binding action, themicroswitch 164 will remain open which will prevent the light 175 frombeing illuminated. Since the operator is able to detect that the light175 is not illuminated, he or she will know that the locking pins havenot been fully retracted. The operator then jiggles or jogs the traileras previously described to loosen the binding on the locking pins. Whenthe locking pins 74 have been completely retracted, pin 130 will be inthe position illustrated in FIG. 6 which will cause switch arm 172 to bedeflected thereby closing switch 164 to illuminate light 174 whichprovides a signal to the driver that the locking pins 74 have beenretracted.

When the locking pins 74 have been retracted and the frame of thetrailer body moved with respect to the slider, air valve 174 isde-energized by switch 184 which causes the air in the cylinder 102 tobe exhausted through the valve 174 by means of the exhaust port 176. Thesprings 84 on the locking pins 74 then cause the locking pins 74 to movefrom their retracted positions to their extended positions.

When the locking pins 74 have been properly positioned in their extendedand locked position, the operator then moves the lever 192 to releasethe brakes on the trailer so that the trailer may be operated in itsnormal condition.

Although the structure described hereinabove solves the problemsassociated with the prior art, it has been found that an additionaladvantage may be achieved in the adjustment of the suspension systemrelative to the trailer body if the operator is somehow able toascertain the amount of movement which has been accomplished during theadjustment process. For example, if the locking pins are in a particularset of openings, the operator knows that the movement of those lockingpins from that set of openings to the next adjacent set of openings willchange the weight distribution of the trailer a certain amount, forexample 250 pounds. Thus, if the operator determines that he/she mustmake a weight distribution adjustment of 750 pounds, the operator knowsthat the trailer body must be moved three openings forwardly orrearwardly, depending upon whether the operator desires to shiftadditional weight from the trailer to the tractor or vice versa.

Heretofore, prior to the instant invention, once the locking pins havebeen retracted, the operator either drives the trailer forwardly orrearwardly with respect to the suspension, which is braked againstmovement, until the operator believes that the proper amount of relativemovement has been achieved. The operator must then exit the cab and makea visual inspection of the locking pins to see if they are in alignmentwith the proper openings in the side rails. Quite often, the lockingpins are not in proper alignment which requires that the operator returnto the cab to attempt to move the trailer body into the proper positionrelative to the suspension. The operator must then again exit the caband make the necessary visual inspection. This process may be repeatedseveral times until the proper alignment is achieved.

To solve the above problem, a position sensing apparatus has beenprovided which is generally referred to by the reference numeral 200.Apparatus 200 includes an elongated support 202 which is secured to theunderside of at least a pair of the cross frame members 14 so that itslongitudinal axis is aligned with the longitudinal axis of the trailer.Support 202 is provided with a plurality of horizontally spaced-apartshoulders or lugs 204 mounted thereon which extend downwardly therefrom.The spacing between the shoulders 204 will correspond to the spacingbetween the openings 82. A conventional, normally closed microswitch 206is mounted on the frame 36 of slider 16 for movement therewith. Switcharm 208 extends from microswitch 206 beneath support 202 and between theshoulders 204.

When one of the shoulders 204 engages the switch arm 208, as the trailerbody is moved with respect to the suspension 18, switch arm 208 isdeflected to open microswitch 206 as illustrated by broken lines in FIG.9.

As seen in FIG. 8, normally closed microswitch 206 is operativelyelectrically connected to microswitch 164. When the locking pins 74 arein their respective openings, microswitch 206 is closed so thatelectrical current is supplied to the "hot" side of microswitch 164.When the locking pins 74 have moved to their retracted positions, light175 is illuminated which indicates that the locking pins 74 are fullyretracted as described hereinabove. The operator then slowly moves thetrailer body with respect to the slider 16. Each time one of theshoulders 204 engages switch arm 208, which means that the trailer hasbeen moved a distance corresponding to the distance between a pair ofopenings 80, microswitch 206 is opened which interrupts the electricalcircuit to microswitch 164 thereby causing light 175 to be deactivated.The deactivation of the light 175 is a signal to the operator that thetrailer has been moved a distance corresponding to the distance betweena pair of openings 80 as described. The continued movement of thetrailer body, with respect to suspension 18 with cause the light 175 toagain be illuminated since switch arm 208 will disengage from theshoulder 204.

Thus, if the operator has determined that the trailer must be adjustedfour openings 80 from the previous position, the operator will move thetrailer body; with respect to the suspension 18, until he/she hasobserved the deactivation of light 175 a total of four times. Thelocking pins 74 may then be extended to their desired locked position.

The successive deactivation of the light 175 by the microswitch 206provides a convenient means for the operator to readily adjust thetrailer body-suspension without the necessity of making one or moretrips from the cab to the rear of the trailer to ascertain whether thetrailer has been moved to the desired position with respect to thesuspension. Thus it can be seen that the invention accomplishes at leastall of its stated objectives.

I claim:
 1. A slider for adjustment of the suspension of a vehiclelongitudinally with respect to the body of the vehicle, the slidercomprising a pair of side rails adapted to be secured to the left andright sides of the body in a fixed position extending longitudinally ofthe body, each of said side rails having a plurality of horizontallyspaced openings formed therein, a frame adapted to carry the suspensioncomprising left and right slide members slidable longitudinally of thebody on the side rails, at least one locking pin operatively mounted oneach of said slide members for longitudinal movement therewith relativeto said side rails, said locking pins being retractable for permittingadjustment of the frame to a selected position of adjustment andextensible into one of said openings in said side rails for locking theframe in a selected position of adjustment, actuator means forretracting said locking pins including a movable actuator movablebetween a first and second position and a linkage interconnecting saidmovable actuator and said pins for conjoint movement of the pins betweenextended and retracted positions, the improvement comprising:sensingmeans for sensing the relative longitudinal movement of said vehiclebody with respect to said vehicle suspension; a signal means operativelyconnected to said sensing means, said signal means being operated toprovide a signal to the vehicle operator that the vehicle body has beenmoved a predetermined amount with respect to said vehicle suspension; anormally open first switch in the path of said movable actuator which isclosed by said movable actuator when said movable actuator is moved fromits said first position to its said second position; said signal meanscomprising a light operatively connected to said first switch which isnormally illuminated when said movable actuator has been moved to itssaid second position and said locking pins have been moved to theirretracted positions.
 2. The slider of claim 1 wherein said light ispositioned at one side of said vehicle body.
 3. The slider of claim 1wherein said sensing means also comprises a second switch which isoperated as said vehicle body is successively moved, in predeterminedamounts, relative to said vehicle suspension.
 4. The slider of claim 3wherein said second switch is operated each time one of the retractedlocking pins moves into alignment with one of said openings in theassociated side rail.
 5. The slider of claim 1 wherein said sensingmeans further comprises an elongated member secured to said vehicle bodyfor movement therewith; said elongated member having its longitudinalaxis disposed in alignment with the longitudinal axis of said vehiclebody; said elongated member having a plurality of horizontallyspaced-apart shoulders provided thereon which are spaced correspondingto the spacing between said openings in said side rails; a second switchmounted on said slider for movement therewith and having a switch armextending therefrom which is successively engaged and moved by saidshoulders as said vehicle body is longitudinally adjusted relative tosaid vehicle suspension; said second switch being connected to saidlight to control the operation of said light each time said switch armis moved by its engagement with one of said shoulders as said vehiclebody is moved relative to said vehicle suspension.
 6. The slider ofclaim 5 wherein said second switch interrupts the electrical circuit tosaid light to deactivate said light each time said locking pins moveinto alignment with one of said openings as said vehicle body is movedwith respect to said vehicle suspension.